joining me now, nbc's chief science and health correspondence, bob bazell. and also with me "the washington post" ruth marcus. first to you, where this clot was found, a follow-up mri we were told on sunday night, and we were told it was a clot stemming from the concussion from the fall. does that mean that the clot was necessarily caused by the concussion or could it be from an underlying condition, or is there no way to really know that fact? >> it may have been caused by both of those problems. sometimes there's sort of a perfect storm of issues going on with any individual patient, with potential histories of history of blood clots in the past, as well as head trauma. this can increase the risk of getting a blood clot in that part of the brain. >> let me ask you also about how potentially dangerous this is. we know that this is near the brain, not in the brain, it is in the area between the skull and the brain. it is behind the right ear, we're told. we don't know a whole lot more. we are told today the secretary is on with her staff, so she is making ca